Failures can occur for many reasons, but experience has shown that certain causes of failure fall into fairly distinct categories.
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Shipping and handling damage. Examples: Denting or gouging of bellows from being struck by hard objects (tools, chain falls, forklifts, adjacent structures, etc.); improper stacking for shipping or storage; insufficient protection from weather or other adverse environmental conditions.
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Improper installation and insufficient protection.
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During and after installation.
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Examples: Joints with internal liners installed in the reverse direction with respect to flow; installing an expansion joint in a location other than as prescribed by the installation drawings; premature removal of shipping devices; springing of bellows to make up for piping misalignment; insufficient protection from mechanical damage due to work in the surrounding area; insufficient protection of bellows during nearby welding operations and failure to remove shipping devices before placing system in operation.
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Improper anchoring, guiding and supporting of the system.
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Anchor failure in service.
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Bellows corrosion, both internal and external.
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System over-pressure (in-service or hydrotest). Bellows vibration (mechanical or flow-induced resulting in high cycle fatigue).
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Excessive bellows deflection (axial, lateral, angular deflections greater than design values).
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Torsion.
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Bellows erosion.
- Packing of particulate matter in the bellows convolutions which inhibits proper movement of the bellows.
